如果我们只有一个成员，结构和联合之间有什么区别吗？ [英] Is there any difference between structure and union if we have only one member?

问题描述

我想知道一种成员数据类型在结构和联合之间的区别（如果有的话）。

I would like to know the difference between structure and union for one member data type if there is any.

推荐答案

在C：没有。著名的节省空间的笑话 #define struct union 几乎不是笑话。

In C: None. The famous "space-saving joke" #define struct union is almost not a joke.

在C ++中98：联盟只能具有 POD成员，非联盟类可以具有任意成员。

In C++98: Unions can only have POD members, non-union classes can have arbitrary members.

在C ++ 11中：联合可以具有对象类型（但不是引用类型）的任意数据成员，但与非联合类相比，它们的使用受到更多限制。 （即：联合不能具有虚拟成员函数，不能是基类并且不能具有基类。）而且，与单成员非联合类相比，您必须编写更多代码以使单成员联合工作。 ，因为您必须自己编写构造函数和析构函数。

In C++11: Unions can have arbitrary data members of object type (but not of reference type), but their use is more restricted that that of non-union classes. (Namely: a union cannot have virtual member functions, cannot be a base class and cannot have base classes.) Also, you have to write more code to make a one-member union work as opposed to a one-member non-union class, since you have to write constructors and the destructor yourself.

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